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| United States Patent |
5,733,283
|
|
Malis
, et al.
|
March 31, 1998
|
Flat loop bipolar electrode tips for electrosurgical instrument
Abstract
An electrode tip is provided for use in a bi polar electrosurgical
instrument. The electrode tip has a generally loop shaped working portion,
including a first and second electrode, The first electrode is generally
loop shaped. The second electrode generally surrounds the first electrode
and is generally spaced from and coplanar with the first electrode. The
electrodes have sharp edges in cross-section which emit concentrated
energy in the radial direction.
| Inventors:
|
Malis; Jerry L. (300 Valley Forge Cir., Penthouse 43, King of Prussia, PA 19406);
Mortimer; Martin T. (41 Indian Valley La., Telford, PA 18969);
Malis; Leonard (219-44 Peck Ave., Queens, NY 11427)
|
| Appl. No.:
|
658429 |
| Filed:
|
June 5, 1996 |
| Current U.S. Class: |
606/48; 606/50 |
| Intern'l Class: |
A61B 017/39 |
| Field of Search: |
606/41,45,46,48-50,29,30
219/233,236-239
|
References Cited
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|
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| |
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|
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| |
Other References
Brochure entitled "Photo Chemical Machining", Buckbee-Mears, St. Paul, A
Unit of BMC Industries, Inc., St. Paul, MN, 1995, 2 pages.
|
Primary Examiner: Cohen; Lee S.
Attorney, Agent or Firm: Panitch Schwarze Jacobs & Nadel, P.C.
Claims
We claim:
1. An electrode tip for an electrosurgical instrument, the electrode tip
comprising an electrode, the electrode having a working portion that is
generally loop shaped and has sharp edges in cross-section, the working
portion being generally rectangular in cross-section and circumferentially
unattached to any surrounding structure, wherein the working portion has a
cross-sectional width of about 0.15 mm or about 0.23 mm.
2. An electrode tip according to claim 1 wherein the generally loop shaped
working portion of the electrode is generally circular, semicircular,
parabolic or rectangular in shape.
3. An electrode tip according to claim 1 wherein the electrode is formed
from the group of materials consisting of stainless steel, tungsten, a
nickel and chromium alloy and titanium.
4. An electrode tip according to claim 1 wherein the electrode has
cross-sectional thickness of about 0.13 mm to about 0.38 mm.
5. An electrode tip according to claim 1 wherein the area of the
rectangular cross-section is generally uniform throughout the working
portion.
6. An electrode tip according to claim 1 wherein the electrode material is
continuous through the working portion.
7. An electrode tip for an electrosurgical instrument comprising:
(a) a first electrode having a working portion that is generally loop
shaped and has sharp edges in cross-section; and
(b) a second electrode having a working portion that is generally loop
shaped and has sharp edges in cross-section, the second electrode
generally surrounding at least a part of the working portion of the first
electrode, the second electrode being generally spaced from and coplanar
with the first electrode.
8. An electrode tip according to claim 7 wherein the first and second
electrodes are generally rectangular in cross-section.
9. An electrosurgical instrument according to claim 7 wherein the spacing
between the working portions of the first and second electrodes is
generally equal along the entire length of the working portions.
10. An electrode tip according to claim 7 wherein the first electrode is a
closed loop.
11. An electrode tip according to claim 7 wherein the second electrode is
an almost closed loop.
12. An electrode tip according to claim 7 wherein the first electrode is a
closed loop and the second electrode is an almost closed loop.
13. An electrode tip according to claim 7 wherein the generally loop shaped
working portion of the first and second electrodes are generally circular,
semicircular, parabolic or rectangular in shape.
14. An electrode tip according to claim 7 wherein the first and second
electrodes are formed from the group of materials consisting of stainless
steel, tungsten, a nickel and chromium alloy, and titanium.
15. An electrosurgical instrument comprising:
(a) a handle having a proximal end and a distal end; and
(b) an electrode tip, the tip including
(i) a first electrode extending from the distal end, the first electrode
having a working portion that is generally loop shaped and is generally
rectangular in cross-section, the first electrode adapted to be connected
to one pole of a bipolar generator, and
(ii) a second electrode extending from the distal end, the second electrode
having a working portion that is generally loop shaped and is generally
rectangular in cross-section, the second electrode adapted to be connected
to the other pole of the bipolar generator, the second electrode generally
surrounding at least a part of the working portion of the first electrode,
the second electrode being generally spaced from and coplanar with the
first electrode.
16. An electrosurgical instrument according to claim 15 further comprising:
(c) first and second conductors each connected at one end to the respective
first and second electrodes and adapted for being connected at the other
end to the respective poles of the bipolar generator, the first and second
conductors extending through the handle from the proximal end to the
distal end.
17. An electrosurgical instrument according to claim 15 wherein the spacing
between the working portions of the first and second electrodes is
generally equal along the entire length of the working portions.
18. An electrosurgical instrument according to claim 15 wherein the first
electrode is a closed loop.
19. An electrosurgical instrument according to claim 15 wherein the second
electrode is an almost closed loop.
20. An electrosurgical instrument according to claim 15 wherein the first
electrode is a closed loop and the second electrode is an almost closed
loop.
21. An electrosurgical instrument according to claim 15 wherein the
generally loop shaped working portion of the first and second electrodes
are generally circular, semicircular, parabolic or rectangular in shape.
22. An electrosurgical instrument according to claim 15 wherein the first
and second electrodes are formed from the group of materials consisting of
stainless steel, tungsten, a nickel and chromium alloy, and titanium.
23. An electrosurgical instrument according to claim 15 further comprising:
(c) an irrigation conduit extending through the handle from the proximal
end to the distal end for delivering irrigation fluid to the distal end.
24. An electrosurgical instrument according to claim 15 wherein the first
and second electrodes include non-working portions, the instrument further
comprising:
(c) a tip mounting for maintaining the first and second electrodes in the
spaced relationship and for attaching the electrode tip to the handle, the
tip mounting formed from first and second generally T-shaped pieces of
material attached to each other, at least a part of the non-working
portions of the first and second electrodes being sandwiched between the
first and second T-shaped pieces of material, a vertical portion of the
tip mounting being attached to the handle.
25. An electrosurgical instrument comprising:
(a) a handle having a proximal end and a distal end; and
(b) an electrode tip, the tip including
(i) a first electrode extending from the distal end, the first electrode
having a working portion that is generally loop shaped and is generally
rectangular in cross-section, the first electrode adapted to be connected
to one pole of a bipolar generator, and
(ii) a second electrode extending from the distal end, the second electrode
being generally hook shaped and having a working portion that is generally
rectangular in cross-section, the second electrode adapted to be connected
to the other pole of the bipolar generator, the second electrode generally
hooking around the first electrode, the second electrode being generally
spaced from and coplanar with the first electrode.
26. An electrosurgical instrument according to claim 25 wherein the second
electrode hooks almost completely around the first electrode.
27. An electrode tip for an electrosurgical instrument, the electrode tip
comprising an electrode, the electrode having a working portion that is
generally loop shaped and has sharp edges in cross-section, the electrode
having only one end adapted to be connected to a conductor, and the
working portion being circumferentially unattached to any surrounding
structure.
28. An electrode tip according to claim 27 wherein the electrode is
generally rectangular in cross-section.
29. An electrode tip according to claim 27 wherein the electrode material
is continuous through the working portion.
30. An electrosurgical instrument comprising:
(a) a handle having a proximal end and a distal end; and
(b) an electrode tip including an electrode extending from the distal end,
the electrode having a working portion that is generally loop shaped and
has sharp edges in cross-section, the electrode including a single lead
section for attachment of the electrode to one pole of a bipolar
generator, and the working portion being circumferentially unattached to
any surrounding structure.
31. An electrosurgical instrument according to claim 30 wherein the
electrode is generally rectangular in cross-section.
32. An electrosurgical instrument according to claim 30 wherein the
electrode material is continuous through the working portion.
33. An electrosurgical instrument comprising:
(a) a handle having a proximal end and a distal end; and
(b) an electrode tip directly connected to, and supported by, the handle,
the electrode tip including an electrode having a working portion that is
generally loop shaped and has sharp edges in cross-section, the working
portion being circumferentially unattached to any surrounding structure,
wherein the working portion has a cross-sectional width of about 0.15 mm
or about 0.23 mm.
34. An electrosurgical instrument according to claim 33 wherein the
electrode is generally rectangular in cross-section.
35. An electrosurgical instrument according to claim 33 wherein the
electrode material is continuous through the working portion.
36. An electrode tip for an electrosurgical instrument, the electrode tip
comprising an electrode, the electrode having a working portion that is
generally loop shaped and has sharp edges in cross-section, the working
portion being generally rectangular in cross-section and circumferentially
unattached to any surrounding structure, wherein the working portion has a
cross-sectional thickness of about 0.13 mm to about 0.38 mm.
37. An electrode tip according to claim 36 wherein the working portion has
a cross-sectional width of about 0.15 mm or about 0.23 mm.
38. An electrode tip according to claim 36 wherein the generally loop
shaped working portion of the electrode is generally circular,
semicircular, parabolic or rectangular in shape.
39. An electrode tip according to claim 36 wherein the electrode is formed
from the group of materials consisting of stainless steel, tungsten, a
nickel and chromium alloy and titanium.
40. An electrode tip according to claim 36 wherein the area of the
rectangular cross-section is generally uniform throughout the working
portion.
41. An electrode tip according to claim 36 wherein the electrode material
is continuous through the working portion.
42. An electrosurgical instrument comprising:
(a) a handle having a proximal end and a distal end; and
(b) an electrode tip directly connected to, and supported by, the handle,
the electrode tip including an electrode having a working portion that is
generally loop shaped and has sharp edges in cross-section, the working
portion being circumferentially unattached to any surrounding structure,
wherein the electrode has a cross-sectional thickness of about 0.13 mm to
about 0.38 mm.
43. An electrosurgical instrument according to claim 42 wherein the
electrode is generally rectangular in cross-section.
44. An electrosurgical instrument according to claim 42 wherein the
electrode material is continuous through the working portion.
Description
FIELD OF THE INVENTION
The present invention relates generally to electrosurgical instruments,
and, in particular to an electrode tip for a bipolar electrosurgical
cutting/coagulating instrument particularly adaptable for use in
constricted areas and a method of making an electrode tip by a photo
chemical machining process.
BACKGROUND OF THE INVENTION
Electrosurgery is one form of a surgical cutting and coagulating procedure.
Electrosurgery has two primary modes--monopolar and bipolar. Monopolar
surgery uses an instrument, with a single electrode such as a single loop
instrument, and a grounding pad as the means to administer the output of a
surgical generator to the patient. In contrast, bipolar instruments
include two electrodes in close proximity to each other. Typically, one
electrode is a supply electrode and the other electrode is a return
electrode. Bipolar instruments operate at much lower power levels than
monopolar instruments and thus do not disturb nearby tissue. Examples of
bipolar instruments are shown in U.S. Pat. Nos. 5,290,286 (Parins);
5,192,280 (Parins); 5,013,312 (Parins et al.); 5,282,799 (Rydell);
5,071,419 (Rydell) and WO 93/13719 (Fleenor et al.).
Wire electrodes, which are used in some such instruments, are generally
rounded in cross-section and thus do not concentrate energy in any
particular radial direction. Rounded electrodes also present a relatively
large contact area to the surgical site. This may be undesirable if the
area of interest is very small. Furthermore, it is difficult to make a
wire electrode which has a very small diameter (i.e., width). The smaller
the diameter, the smaller the cross-sectional area and the finer the
electrode. Finer electrodes make finer cuts. An instrument with very fine
electrodes can be used in tight crevices and in small areas, such as
certain predefined regions of the brain. It is also a desirable goal for
electrodes to have low resistance so that only a small amount of power
need be applied to the electrodes to effectively cut and coagulate the
desired tissue. By using less power at the surgical site, the device can
be used in delicate surgical procedures, such as neurosurgery, with less
risk of damaging neighboring areas.
Despite the variety of electrodes known in the prior art, there is still a
need for a finer electrode which can also concentrate energy in the radial
direction, is easy and inexpensive to fabricate, and has relatively low
resistance. The present invention fills this need by providing an
electrode tip with very fine electrodes that have sharp edges in
cross-section and are preferably fabricated by photo chemical machining.
SUMMARY OF THE INVENTION
The present invention in one embodiment provides an electrode for a
microsurgical instrument. The electrode has a working portion that is
generally loop shaped and has sharp edges in cross-section.
Another embodiment of the invention provides an electrode tip comprising a
first and a second electrode. The first electrode has a working portion
that is generally loop shaped and has sharp edges in cross-section. The
second electrode generally surrounds at least a part of the working
portion of the first electrode and is generally spaced from and coplanar
with the first electrode.
Yet another embodiment of the invention comprises an electrosurgical
instrument having a handle and an electrode tip. The handle has a proximal
end and a distal end. The electrode tip includes a first electrode and a
second electrode. The first and second electrodes each extend from the
distal end and have a working portion that is generally loop shaped and
generally rectangular in cross-section. The first and second electrodes
are adapted to be connected to opposite poles of a bipolar generator. The
second electrode generally surrounds at least a part of the working
portion of the first electrode and is generally spaced from and coplanar
with the first electrode.
Yet another embodiment of the invention comprises a handle and an electrode
tip. The handle has a proximal end and a distal end. The electrode tip
includes a first and a second electrode, each extending from the distal
end, having a working portion that is generally loop shaped and being
rectangular in cross-section. The first and second electrodes are adapted
to be connected to opposite poles of a bipolar generator. The second
electrode is generally hook shaped, generally hooks around the first
electrode, and is generally spaced from and coplanar with the first
electrode.
Yet other embodiments of the invention provide methods of fabricating
electrodes from a metal blank. In one exemplary fabrication method, an
electrode tip is fabricated from a metal blank. The method comprises the
steps of defining a pattern, the pattern including an electrode tip, and
machining the metal blank as defined by the pattern to form at least the
electrode tip. The resultant electrode tip has sharp edges in
cross-section.
In another exemplary fabrication method, an electrode is fabricated from a
metal blank. The method comprises the steps of creating at least one
pattern, the pattern including at least an electrode pattern, placing a
negative of the pattern against opposite facing surfaces of a metal blank
coated with a photoresist material, the negative of the pattern on the
opposite facing surfaces being in registration with each other, exposing
and developing the metal blank, and removing photoresist from unexposed,
undeveloped areas of the metal blank. Next, the metal blank is exposed to
a metal dissolving chemical that etches away the unexposed, undeveloped
areas of the metal blank. The resultant piece of metal is suitable for use
as at least one electrode and has a shape of the at least one created
electrode pattern, and has sharp edges in cross-section.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing summary, as well as the following detailed description of
preferred embodiments of the invention, will be better understood when
read in conjunction with the appended drawings. For the purpose of
illustrating the invention, there are shown in the drawings embodiments
which are presently preferred. It should be understood, however, that the
invention is not limited to the precise arrangements and instrumentalities
shown. In the drawings:
FIG. 1 is a perspective view of an electrosurgical instrument in accordance
with a preferred embodiment of the present invention, shown attached to a
bipolar generator and ready for use;
FIG. 2 is a transverse sectional view of an electrosurgical instrument in
accordance with another preferred embodiment of the present invention,
prior to removal of its protective electrode tip guard;
FIG. 3 is an exploded perspective view of the instrument of FIG. 2;
FIG. 4 is an enlarged perspective view of electrodes used in an electrode
tip for the instrument in FIG. 1;
FIG. 5 is an enlarged top plan view of the electrode tip in FIG. 4 with a
tip mounting superimposed thereon in phantom;
FIG. 6 is an enlarged sectional view of the electrode tip in FIG. 4, taken
through line 6--6 of FIG. 4;
FIG. 7 is a blank of metal showing an electrode tip pattern for making an
electrode tip for the instrument in FIG. 2; and
FIG. 8 shows a plurality of electrode tips for the instrument of FIG. 2,
simultaneously formed from a single metal blank, and prior to being
detached therefrom.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Certain terminology is used herein for convenience only and is not be taken
as a limitation on the present invention. The words "upper," "lower,"
"horizontal" and "vertical" designate directions in the drawings to which
reference is made. In the drawings, the same reference numerals are
employed for designating the same elements throughout the several figures.
FIG. 1 shows an electrosurgical instrument 10 in accordance with a
preferred embodiment of the present invention connected to a radio
frequency (RF) output of a bipolar generator 12. Bipolar generators are
well-known in the prior art, and thus are not described in detail herein.
One bipolar generator suitable for use with the instrument 10 is a CMC III
bipolar generator, manufactured by Valley Forge Scientific Corp., Oaks,
Pa., described in U.S. Pat. No. 5,318,563 (Malis et al.). FIG. 2 shows
internal structure of an instrument 10' and FIG. 3 shows an exploded view
of the main components of the instrument 10'. The instrument 10 shown in
FIG. 1 differs in two minor ways from the instrument 10' shown in FIGS. 2
and 3. First, the instrument 10' includes a guard 26 integrally formed
with the tip of the instrument 10'. The guard 26 is removed before use. In
FIG. 1, the guard 26 has already been removed. The guard 26 is described
in more detail below. Second, the instrument 10 shown in FIG. 1 includes
optional irrigation means, whereas the instrument 10' shown in FIGS. 2 and
3 does not include irrigation means. For clarity, FIGS. 1-3 are described
together.
Referring to FIGS. 1-3, the instruments 10 and 10' include a handle 14 and
an electrode tip 16. The handle 14 has a proximal end 18 and a distal end
20. The electrode tip 16 extends from the distal end 20. The electrode tip
16 includes a "working portion" which is generally forward of imaginary
line 1 and a "non-working portion" or base portion which is generally
behind the imaginary line 1 (see FIGS. 1 and 3). The "working portion"
comprises that area of the electrode tip 16 which may contact a patient to
cut or coagulate. The handle 14 in FIG. 1 is constructed of integrally
joined proximal and distal portions 22 and 24 of a high-impact polymeric
tubing material, such as extruded styrene. The distal portion 24 partially
telescopes into the proximal portion 22 and is secured thereto with
adhesive, such as epoxy or cyanoacrylate. Alternatively, the handle 14 may
be constructed as a unitary piece. The handle 14 may optionally have
circular spaced ribs (not shown) for enhanced gripping. The electrode tip
16 includes a pair of conductive metal electrodes, an outer electrode 30
and an inner electrode 32, both of which include a portion which extends
from the distal end 20 of the handle 14. The structure of the electrodes
30 and 32 is described in more detail below. However, FIG. 3 (and also
FIG. 4) clearly shows that the outer and inner electrodes 30 and 32 are
not physically connected to each other and thus some means are required
for maintaining a desired spacing therebetween. Accordingly, a T-shaped
tip mounting 33 (FIG. 1) of nonconductive material maintains the outer and
inner electrodes 30 and 32 a fixed distance from each other and physically
secures the electrode tip 16 to the distal end of the handle 14. FIG. 3
shows that the tip mounting 33 is formed from two identical T-shaped
pieces of nonconductive material 33a and 33b, portions of the electrode
tip 16 being sandwiched therebetween. That is, portions of the electrode
tip 16 are encased within the tip mounting 33. The imaginary line 1 is
colinear with the front edge of the tip mounting 33.
Still referring to FIGS. 1-3, each of the electrodes 30 and 32 are
connected to one end of a respective insulated conductor which extends
through the handle 14 from the proximal end 18 to near the distal end 20.
Thus, the electrode 30 is connected to one end of a first insulated
conductor 34 and the electrode 32 is connected to one end of a second
insulated conductor 36. The other ends of the first and second conductors
34 and 36 terminate in respective connection pins 38 and 40. The
insulation on opposite ends of the conductors 34 and 36 is removed to
electrically connect the conductors 34 and 36 to the electrodes 30 and 32
at one end, and to the pins 38 and 40 at the other end. Referring to FIG.
1, conductive wires 42 and 44 are connected at one of their ends to the
connection pins 38 and 40, respectively, and are connected at the other of
their ends to opposite poles of an isolated output 48 of the bipolar
generator 12.
The instruments 10 and 10' each include an end cap 46 and 46',
respectively, for sealing the proximal end 18 of the handle tubing and for
supporting the connection pins 38 and 40. The end cap 46 of the instrument
10 includes additional structure to support an irrigation tube associated
with the irrigation means, as described below.
Referring to FIG. 1, an optional irrigation fluid tube 50 extends through
the handle 12 for delivering irrigation fluid to the surgical site. One
end of the fluid tube 50 is connected to a luer adapter (not shown) inside
of the end cap 46. The other end preferably terminates at the distal edge
of the tip mounting 33, preferably extending about 1/16" beyond the tip
mounting surface. The fluid tube 50 enters the tubular handle 14 through
an inlet port 52 near the proximal end 18, and exits the handle 14 through
an outlet port 56 near the distal end 20 (which, when the instrument 10 is
in use, is near the surgical site). The end cap 46 includes an extension
47 with a bore for supporting the irrigation tube 50 at the end of the
handle 10. The luer is inside of the extension 47. Irrigation tubing 51 is
connected at one end to the luer and at the other end to a source of
irrigation fluid (not shown). Irrigation fluid (e.g., saline) from the
fluid source is thus delivered through the tubing 51, luer, and tube 50 to
the surgical site.
To join the electrodes 30 and 32 into a single, unitary electrode tip 16
which can be secured to the handle 14, part of non-working portions of
each of the electrodes 30 and 32 are sandwiched between two nonconductive
T-shaped pieces of material 33a and 33b, best shown in FIG. 3. In a
preferred embodiment of the invention all of the non-working portions are
sandwiched between the pieces of material 33a and 33b, except for terminal
ends of the electrodes 30 and 32. In a preferred embodiment of the
invention, the pieces of material 33a and 33b are plate-like pieces of
polymeric material, ultrasonically bonded to each other, to firmly hold
the electrodes 30 and 32 in a fixed position with respect to each other.
Alternatively, the pieces of material 33a and 33b may be cast ceramic
material held together with adhesive. Together, the pieces of material 33a
and 33b form a tip mounting 33. To mount the electrode tip 16 to the
handle 14, the distal end 20 of the handle 14 is heated to a pliable
state. Next, the vertical portion of the tip mounting 33 is inserted into
the distal end 20. As the distal end 20 cools, it conforms to and grips
the vertical portion of the tip mounting 33. The bond may be further
strengthened with adhesive, such as epoxy or cyanoacrylate.
In another embodiment of the invention, the electrode tip 16 is secured to
a handle without using the tip mounting 33. In this alternative
embodiment, the handle is longitudinally divided into an upper half and
lower half. The portions of the electrode tip 16 behind the imaginary line
1 are seated into grooves formed in the lower half of the handle, and
terminal ends of the two electrodes make positive electrical connection to
respective ends of the conductors 34 and 36. Next, the upper half of the
handle is placed over the lower half and secured thereto. The electrode
tip 16 is thus held in place by being partially seated into the grooves
and sandwiched between the upper and lower halves of the handle. Other
means for securing the electrode tip 16 to the handle are within the scope
of the invention.
FIGS. 4-6 show additional details and parameters of the electrode tip 16,
absent the guard 26 and tip mounting 33. In FIG. 5, the tip mounting 33 is
superimposed on the electrode tip 16 in phantom. As described above, the
electrode tip 16 has a working portion and a base portion. In addition,
each of the electrodes 30 and 32 includes a working portion and a base
portion. The working portions of each electrode include the exposed loop
parts of the electrodes (i.e., the portions of the electrodes 30 and 32
which are external to the tip mounting 33 and forward of the imaginary
line 1). The remaining parts one the electrodes 30 and 32 (the parts
enclosed by the tip mounting 33) define the base portion.
Referring to FIGS. 4 and 5, the electrode 30 includes a working portion 80
and a base portion 82, and the electrode 32 includes a working portion 84
and a base portion 86. The base portion 86 comprises a horizontal section
94 and a lead or vertical section 92. The horizontal section 94 bridges
opposite ends of the looped working portion 84. The vertical section 92 is
connected at one end to the horizontal section 94. The free end of the
vertical section 92 is electrically connected to conductor 36, as shown in
FIGS. 2 and 3. Together, the working portion 84 and horizontal section 94
define a closed loop.
The base portion 82 of electrode 32 comprises L-shaped sections 90 and 91
extending from opposite ends of the looped working portion 80. The
L-shaped section 90 includes a horizontal section 96 and vertical section
97. The L-shaped section 91 also includes a horizontal section 98 and
vertical section 99. The horizontal section 96 is connected at one end to
an end of the looped working portion 80, and at the other end to the
vertical section 97. The free end of the vertical section 97 is used to
secure the electrode 30 in proper registration with the electrode 32 via
the tip mounting 33 and to inhibit horizontal movement of the electrode 30
within the tip mounting 33. The horizontal section 98 is connected at one
end to the other end of the looped working portion 80, and at the other
end to the vertical section 99. The free end of the vertical section 99 is
electrically connected to conductor 34, as shown in FIGS. 2 and 3.
Together, the horizontal sections 96 and 98 and the working portion 80
define an almost closed loop which generally surrounds the closed loop of
the electrode 30. Alternatively, the horizontal sections 96 and 98 and the
working portion 80 may be viewed as defining a hook shape which hooks
almost completely around the closed loop of the electrode 32. Since the
two electrodes 30 and 32 are coplanar and cannot come into electrical
contact with each other, the electrode 30 cannot, by design, form a closed
loop completely around the electrode 32.
FIG. 5 shows a top plan view of the electrode tip 16 in FIG. 4. FIG. 5 also
shows regions of the two electrodes 30 and 32 which are encased within the
tip mounting 33, shown in phantom. As described above, the electrode 30
generally surrounds the electrode 32 and is generally spaced from and
coplanar with the electrode 32. More precisely, either all or at least a
part of the working portion 80 of the electrode 30 surrounds either all or
at least a part of the working portion 84 of the electrode 32. In FIG. 5,
the entire working portion 80 surrounds the entire working portion 84. As
also described above, there is a predetermined distance between the
electrodes 30 and 32. In one preferred embodiment of the invention, the
predetermined distance or spacing, s, is generally equal along the entire
path or shape of the electrodes 30 and 32. In another preferred embodiment
of the invention, the spacing s is equal between the working portions 80
and with different spacings allowed between the base portions 82 and 94.
However, there is always some finite spacing between the electrodes 30 and
32 (i.e., s>0) so that the two electrodes 30 and 32 are never in direct
electrical contact with each other. In the example where the spacing s
between the working portions 80 and 84 of the electrodes 30 and 32 is
equal, it can be said that the electrode 30 is equidistant from the
electrode 32. In the figures, the spacing s is equal along the entire path
of the electrodes 30 and 32. The scope of the invention also includes
embodiments wherein the spacing s between the working portions 80 and 84
of the electrodes 30 and 32 is unequal. For example, the spacing s near
the apex of the arc defined by the working portions may be different than
the spacing s near the edge regions of the working portions. It may be
desirable to have greater or less spacing s near the apex of the arc
defined by the working portions than near the edge regions of the working
portions.
The electrode tip 16 and electrodes 30 and 32 have defined dimensions and
parameters. The tip mounting 33 is shown in FIG. 5 because certain
dimensions of the electrode tip 16 are defined in relationship to the tip
mounting 33, or to other structure that performs the same function as the
tip mounting 33. The maximum horizontal distance of the electrode tip 16
is defined as the width, w.sub.t, of the working portion 84 of the
electrode 32. The width, w.sub.t, is the distance between opposite exposed
ends of the working portion 84 of the electrode 32. The height of the
electrode tip 16 is defined as the height, h.sub.t, from the opposite
exposed ends of the working portion 84 of the electrode 32 to apex 100 of
the arc in the working portion 84 of the electrode 32. (The height of the
electrode tip 16 is thus defined by dimensions of the inner electrode 32,
not the outer electrode 30.) The electrode tip 16 also has a loop ratio,
defined as the ratio of the absolute distance of the working portion 84
vs. the absolute distance of the working portion 80. The leads or vertical
sections 98 and 92 have predefined lengths l.sub.e1 and l.sub.e2,
respectively.
Referring to FIGS. 4, 5 and 6 (especially, FIG. 6), the working portion 80
of the electrode 30 has a flat upper surface 102, a flat lower surface
104, and squared off sharp corners or edges 106. Likewise, the working
portion 84 of the electrode 32 has a flat upper surface 108, a flat lower
surface 110, and squared off sharp corners or edges 112. In the embodiment
of the invention shown in the figures, the base portions 82 and 86 also
have flat upper and lower surfaces, and sharp edges, due to the method of
fabricating the electrodes 30 and 32. The base portions 82 and 86 need not
have either of these features. The working portions 80 and 84 are
circumferentially unattached to any surrounding structure, and the
material of the electrodes 30 and 32 is continuous (i.e., unbroken)
through their respective working portions 84 and 80. As a result of these
features, at least the working portions 80 and 84 of the electrodes 30 and
32 are generally rectangular in cross-section and thus are defined by a
thickness and a width. The area of the rectangular cross-section is
generally uniform throughout the working portion. Since the electrodes 30
and 32 are coplanar, they have equal thicknesses, t.sub.e. The widths of
the electrode working portions 80 and 84 may be equal or different. In the
figures, the electrodes 30 and 32 have different working portion widths
w.sub.e1 and w.sub.e2, respectively. Widths of the horizontal sections 94,
96 and 98, and the leads or vertical sections 92 and 99 are significantly
larger than the widths of the working portion 80 and 84. A preferred
embodiment of the electrode tip 16, has the following approximate range of
dimensions and parameters:
______________________________________
spacing, (s) 0.035" (0.89 mm.)
width of electrode tip (w.sub.t)
0.20" to 0.98" (5 mm. to 25 mm.)
height of electrode tip (h.sub.t)
0.20" to 0.59" (5 mm. to 15 mm.)
length of vertical section 99 (l.sub.e1)
0.50" (12.7 mm.)
length of vertical section 92 (l.sub.e2)
0.54" (13.6 mm.)
loop ratio 1:11/2
thickness of electrodes (t.sub.e)
0.005" to 0.015" (0.13 mm.
to 0.38 mm.)
width of electrode 30 (w.sub.e1)
0.009" (0.23 mm.)
width of electrode 32 (w.sub.e2)
0.006" (0.15 mm.)
width of horizontal sections 90,
0.059" (1.5 mm.)
94 and 96
width of vertical sections 92 and 98
0.039" (1.0 mm.)
electrode 30 and 32 material
stainless steel, tungsten, titanium,
tungsten deposited on stainless
steel, INCONEL, (a nickel and
chromium alloy) or other metallic
alloys
______________________________________
Some examples of suitable width and height combinations for electrode tips
include 25.times.15, 20.times.10, 20.times.7, 15.times.10, 15.times.7,
10.times.10, 10.times.7, 5.times.10, 5.times.5 and 3.times.5, wherein the
first dimension is the width (w.sub.t) in mm. and the second dimension is
the height (h.sub.t) in mm. FIGS. 4-6 show a 20.times.10 mm. tip having a
thickness of about 0.015" (0.38 mm.).
One preferred method of fabricating the electrode tip 16 is by photo
chemical machining. Referring to FIG. 7, the process begins with a metal
blank 114, such as stainless steel, having a thickness t.sub.e and flat
upper and lower surfaces 116 and 118. The metal blank 114 is precoated
with photoresist materials of common usage. A pattern 120 and its mirror
image 120' are created by standard drafting techniques and are
photographically transferred (in negative form) to transparent film. The
patterns 120 and 120' may also be reduced in size to reduce drawing line
widths and to achieve proper final product size. Next, properly sized
patterns 120 and 120' are placed in contact with respective upper and
lower surfaces 116 and 118 of the metal blank 114, in proper registration
and alignment with each other. The pattern 120 on the upper surface 116 is
in solid lines and the pattern 120' on the lower surface 118 is in
phantom. Using a vacuum table (not shown), the upper and lower patterns
120 and 120' are held closely to the metal blank 114 while an arc lamp 121
exposes the photoresist in the area where the negative patterns are
transparent. Next, the metal blank 114 is removed and developed in the
same manner as a negative photograph is developed. The developing process
chemically hardens the photoresist in areas exposed to the arc lamp 121.
The unexposed and undeveloped photoresist is washed away. Next, the metal
blank 114 is exposed to chemicals commonly used in the art to dissolve
metal not covered with photoresist. Chromic acid, ferric chloride, or
other etch chemicals may be used. After etching, the remaining metal is a
faithful reproduction, in metal, of the pattern 120, including at least
the electrodes, a carrier and a protective guard structure, and support
and tab structures, all for use during post-manufacturing handling. For
simplicity, FIG. 7 does not show the patterns which form the additional
non-electrode structures. These patterns are shown in FIG. 8.
The resultant piece of metal has the shape of the created pattern, and is
thus identical to FIGS. 4 and 5. That is, the resultant piece of metal is
the shape of the electrodes 30 and 32. Since the metal blank 114 has flat
upper and lower surfaces 116 and 118, the resultant electrodes 30 and 32
are coplanar and have sharp edges in cross-section. The resultant
electrode tip 16 (i.e., electrodes 30 and 32) is mounted or inserted into
the distal end 20 of the handle 14 and engages conductors 34 and 36 to
establish positive electrical contact therebetween, as shown in FIG. 3, to
create the electrosurgical instrument 10.
The electrode tip 16 is very delicate and should be protected from physical
contact until it is ready to be used. Also, the relative registration of
the electrodes 30 and 32 must be maintained because the two electrodes are
not physically connected to each other at any point. To protect the
electrode tip 16 and to maintain proper relative registration between the
electrodes 30 and 32, it is preferred to fabricate the electrode tip 16
with a guard, supports, a carrier and tabs therebetween, and to install
the tip mounting 33 after fabrication but before removal of the supports
124 or guard 26.
When electrode tips 16 are made by the process described above, plural
electrode tips 16 of the same or different width and height combinations
may be simultaneously fabricated from a single metal blank. Thus,
significant manufacturing efficiencies can be achieved.
FIG. 8 shows eight electrode tips 16.sub.1 through 16.sub.8 fabricated from
a single metal blank 115 and illustrates all of these above-mentioned
features. In FIG. 8, each electrode tip 16.sub.1 through 16.sub.8 has a
different width and height combination. Prior to being etched, a pattern
including (1) a peripheral carrier pattern, (2) an electrode pattern for
each of the electrode tips 16.sub.1 through 16.sub.8, and (3) associated
support patterns, tab patterns and a guard pattern for each electrode
pattern, is placed against both surfaces of the metal blank 115, as
described above. The patterns form the electrode tips 16.sub.1 through
16.sub.8, peripheral carrier 122, support plates or supports 124, guards
26 and tabs 128 in the resultant metal blank of FIG. 8. To install a
particular electrode tip 16 into a handle 14, an electrode tip 16 and
corresponding supports 124 and guard 26 is removed from the carrier 122.
Next, non-working portions of the electrode tip 16 are sandwiched between
the two T-shaped pieces of material 33a and 33b. The pieces of material
33a and 33b are secured to each other and to the electrode tip 16, such as
by ultrasonic bonding to form the tip mounting 33. (Alternatively, the
non-working portions of the electrode tip 16 may be sandwiched between the
two T-shaped pieces of material 33a and 33b while the electrode tip 16 is
still in the carrier 122.) The tip mounting 33 encases all but the working
portion of the electrode tip 16 and the terminal ends of each individual
electrode. As a result, the tip mounting 33 maintains relative
registration of the working portions of the two electrodes. Next, the
supports 124 and related tabs 128 are removed. One end of the first and
second conductors 34 and 36 are connected to respective terminal ends of
the electrodes 30 and 32, such as by soldering or welding. The conductors
34 and 36 are fitted through the distal portion of the handle 14. The
electrode tip 16, with the guard 26 still intact, is then installed into
the distal end of the distal portion 24 of the handle 14, in accordance
with the procedure described above with respect to FIGS. 1-3. FIG. 2 shows
one such guard 26 attached to the electrode tip 16 of a fully assembled
instrument 10. Immediately before use, the guard 26 is snapped off.
While the photo chemical etching process is used to fabricate the entire
electrode tip 16 in one step, the method may be used to separately
fabricate each electrode 30 and 32. The photo chemical etching process may
be replaced by other processes which can achieve a similar result from a
metal blank. Other potential techniques include laser cutting, mechanical
microcutting techniques or other techniques which can form electrodes
having sharp edges and working portion dimensions defined above.
When fabricating electrode tips by the process shown in FIG. 8, the tips
may be colored to quickly identify different sized electrodes. For
example, titanium electrodes tips may be colored by anodizing.
Electrode tip sizes are selected according to the desired application
(e.g., neurosurgery, obstetrics/gynecology surgery) and structure of the
surgical site. For example, a long, narrow tip should be used when the
surgical site is a narrow cavity.
The guard 26 may be replaced by other guard structure which need not be
integrally formed with the electrode tip 16. It is also within the scope
of the invention to make the electrodes 30 and 32 without the carrier 122,
supports 124, guards 26 and tabs 128. Instead, the electrodes 30 and 32
may be carefully handled after fabrication and secured in a fixed
relationship to each other, and to a handle, by other suitable means.
The instrument 10 is meant to be disposable, although it is within the
scope of the invention to reuse any parts of the instrument 10 which are
not degraded during use and which can be adequately sterilized.
The loop shaped working portion of the electrodes 30 and 32 may be
generally circular, semicircular, parabolic or rectangular in shape.
The electrodes 30 and 32 in the present instrument have sharp edges 106 and
112 in cross-section, in contrast to prior art wire electrodes which do
not have sharp edges in cross-section. The sharp edges concentrate the
contact area and improve the concentration of energy at the surgical site
in comparison to the wire electrodes. In use, when power is applied to the
electrode tip 16, energy distributes evenly along the length of the
electrode working portions 80 and 82. The energy also emits radially from
the working portions 80 and 82. However, the emitted RF energy
concentrates and focuses at the edges 106 and 112 instead of radially
emitting equally in all directions as in prior art wire electrodes. For at
least this reason, the electrodes 30 and 32 formed by the process
described above evidence lower resistance to cutting than the prior art
wire electrodes. Thus, less power may be applied to the electrodes 30 and
32 to achieve the same cutting/coagulating effect as the prior art wire
electrodes. By using less power at the surgical site, the device can be
used in delicate surgical procedures, such as neurosurgery, with less risk
of disturbing neighboring tissue or organs.
Furthermore, the electrodes 30 and 32 may be fabricated to be significantly
finer than what is currently achievable using wire electrodes. For
example, the smallest disclosed wire diameter in U.S. Pat. Nos. 5,282,799
(Rydell) and 5,192,280 (Parins) is 0.010 inches (0.254 mm.), providing a
cross-sectional area of 0.05 mm.sup.2 (0.7854.times.d.sup.2
=0.7854.times.(0.254).sup.2 =0.05). In contrast, electrode 30 may have a
width as small as about 0.006" (0.15 mm.) and a thickness as small as
0.005" (0.13 mm.), thereby providing a cross-sectional area as small as
about 0.02 mm.sup.2 (w.times.t=0.15.times.0.13=0.02), measurably finer
than the cross-sectional area of the wire electrode.
Referring to FIG. 6, the electrodes 30 and 32 are ideally rectangular in
cross-section. However, it is difficult to produce perfectly rectangular
shaped electrodes using the chemical etching process described herein. The
fabricated electrodes may have regions of slight concavity along the side
edges, giving a slightly hourglass shape to the electrodes in
cross-section. Such electrodes still possess the advantages described
above because they still have relatively sharp edges. One way to minimize
the concavity when etching from one side only is to etch about halfway
through the blank, and then turn the blank over and etch through the other
side.
It will be appreciated by those skilled in the art that changes could be
made to the embodiments described above without departing from the broad
inventive concept thereof. It is understood, therefore, that this
invention is not limited to the particular embodiments disclosed, but it
is intended to cover modifications within the spirit and scope of the
present invention as defined by the appended claims.
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